Systems and techniques for heating urea injection systems

ABSTRACT

A reductant delivery system is provided for delivery of reductant to an engine exhaust aftertreatment system that is heated during cold temperature conditions. A heat exchange fluid flows through a heat exchange circuit that provides a flow path from the heat source to the doser, from the doser to the reductant storage tank, and from the reductant storage tank to the heat source. A control valve controls the flow of the heat exchange fluid in the heat exchange circuit so that at least one heat exchange cycle includes a circulation period that increases the temperature of the reductant in the doser and storage tank and a termination period where circulation is stopped until reductant temperature in the doser reaches a lower limit.

BACKGROUND

Selective catalytic reduction (“SCR”) exhaust aftertreatment systems arean important technology for reducing NOx emissions from internalcombustion engines such as diesel engines. SCR systems generally includea source of storage for the urea solution, a doser that includes atleast one of a pump unit for pressurizing the urea solution and ametering unit for providing a controlled amount or rate of urea solutionto an SCR catalyst, and an injector which provides urea solution to aurea decomposition region of an exhaust flow path located upstream froman SCR catalyst. Many SCR systems also utilize pressurized gas to assistthe flow of urea solution to the injector. While providing importantreductions in NOx emissions, SCR systems suffer from a number ofshortcomings and problems. For example, the storage tank and doser aretypically mounted to the chassis of the vehicle, and are exposed toambient temperature. In cold weather conditions, the urea solution canfreeze or be too cold to function effectively in the storage tank and/ordoser. While various approaches have been implemented to heat the ureasolution, such approaches are typically complex and expensive, and/orinvolve the independent supply of heat to each of the portions of theSCR system through the use of multiple flow paths and valves in theheating distribution system and/or the use of electric heaters. Thus,there is a need for advancements mitigating these and other shortcomingsassociated with heating delivery systems for a reductant such as a ureasolution.

SUMMARY

Certain exemplary embodiments include systems and techniques for thermalmanagement of at least a storage tank and a doser of a reductantdelivery system for an SCR catalyst. In one embodiment, the systemincludes a heat exchange circuit connected to a heat source, and theheat exchange circuit defines a flow path that is routed from the heatsource to the doser, from the doser to the storage tank, from thestorage tank to the doser, and from the doser to the heat source. Acontrol valve is provided in the flow path to regulate a flow of heatexchange fluid in the flow path. In one particular embodiment, thecontrol valve is located in the flow path after the storage tank.

In another embodiment, the system includes a heat exchange circuitconnected to a heat source and the heat exchange circuit provides a flowpath for a heat exchange fluid. The flow path is routed from the heatsource to a doser and then to a storage tank to provide thermal contactof the heat exchange fluid with the reductant in the doser and thestorage tank. The system further includes a control valve in the heatexchange circuit and a controller operably connected to the controlvalve. The controller is configured to modulate the control valvebetween a first position allowing flow of the heat exchange fluid in theflow path and a second position preventing flow of the heat exchangefluid in the flow path.

In embodiments of the system and method, the controller controlsoperation of the control valve to open and close the control valve toincrease the temperature of the reductant in the storage tank from oneheat exchange cycle to the next heat exchange cycle while maintainingthe temperature of the reductant in the doser between upper and lowertemperature thresholds. In certain embodiments, the system and methodinclude a heat exchange cycle that includes a circulation period of theheat exchange fluid that is initiated by opening the control valve toheat the reductant in the doser to an upper temperature limit whileincreasing the temperature of the reductant in the storage tank, and atermination period that is initiated by closing the control valve to endthe first circulation period to allow the reductant in the doser to coolat a first rate to a lower temperature limit while the reductant in thestorage tank cools at a second rate that is slower than the first rate.When the reductant in the doser reaches the lower temperature limitindicating the end of the termination period and the first heat exchangecycle, a second heat exchange cycle can be initiated with a secondcirculation period started by opening the control valve to heat thereductant in the doser and to heat the reductant in the storage tank.The heat exchange cycles are repeated until the reductant in the storagetank reaches a predetermined temperature threshold. Further aspects,embodiments, forms, features, benefits, objects, and advantages shallbecome apparent from the detailed description and figures providedherewith.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an exemplary reductant delivery andheating system.

FIG. 2 is a diagrammatic view of an exemplary controller of thereductant delivery and heating system.

FIG. 3 is a flow diagram of an exemplary reductant heating procedure.

FIGS. 4A-4D are diagrams showing an exemplary operation of the reductantheating procedure to heat the reductant delivery system over a timeperiod.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, any alterations and further modificationsin the illustrated embodiments, and any further applications of theprinciples of the invention as illustrated therein as would normallyoccur to one skilled in the art to which the invention relates arecontemplated herein.

With reference to FIG. 1 there is illustrated an exemplary system 100for heating of a reductant that is delivered to an exhaust system 104 ofan engine 102 from a reductant delivery system 110. System 100 may beprovided on a vehicle powered by engine 102 such as a diesel engine, oron an engine 102 utilized in other applications such power generation orpumping systems. Engine 102 includes an intake system 112 through whichcharge air enters and an exhaust system 104 through which exhaust gasresulting from combustion exits, it being understood that not alldetails of these systems that are typically present are shown. Engine102 includes a number of cylinders forming combustion chambers intowhich fuel is injected by fuel injectors to combust with the charge airthat has entered through intake system 112. The energy released bycombustion powers the engine via pistons connected to a crankshaft. Whenused to propel a vehicle, engine 102 is coupled through a drivetrain todrive wheels that propel the vehicle. Intake valves control theadmission of charge air into the cylinders, and exhaust valves controlthe outflow of exhaust gas through exhaust system 104 and ultimately toatmosphere. Before entering the atmosphere however, the exhaust gas istreated by one or more aftertreatment devices in an aftertreatmentsystem 108.

In one example, the exhaust system 104 includes an aftertreatment system108 having one or more SCR catalysts 106 and one or more locations forreceiving a reductant from reductant delivery system 110. Theaftertreatment system 108 may include one or more other aftertreatmentcomponents not shown, such as one or more oxidation catalysts, one ormore particulate filters, an ammonia oxidation catalyst, and varioustemperature, pressure and exhaust gas constituent sensors. Exhaustsystem 104 may also include various components not shown, such an EGRsystem, a turbocharger system, coolers, and other components connectingexhaust system 104 to intake system 112. A reductant injector 118 ismounted on a portion of exhaust system 104 upstream of SCR catalyst 106with its outlet, or nozzle, arranged to spray aqueous reductant into theexhaust system where it mixes with engine exhaust gas produced by engine102. SCR catalyst 106 promotes a chemical reaction between the reductantand NOx in the exhaust gas that converts substantial amounts of NOx toreduce NOx emissions before the exhaust gas passes into the atmosphere.

Reductant delivery system 110 further includes a doser 114 that receivesreductant from a storage tank 116 and provides the reductant to injector118 or other structure for injection or delivery to a decompositionchamber or directly to the exhaust system 104. As used herein, injectorincludes any nozzle, static device, electronically controllable device,and/or mechanical actuator that provide an outlet for reductantdelivery. One example of a reductant is a diesel exhaust fluid (DEF)which comprises a solution of 32.5% high purity urea and 67.5% deionizedwater. It shall be appreciated, however, that other reductants may alsobe utilized.

Doser 114 may include various structures to facilitate receipt ofreductant from storage tank 116 and the delivery of the reductant to theexhaust system 104. For example, doser 114 may include a pump and afilter screen and a check valve upstream of the pump to receivereductant from the storage tank 116. In one form the pump is a diaphragmpump, though it shall be appreciated that other types of pumps may beutilized. The pump outputs pressurized reductant at a predeterminedpressure which flows through a second check valve, a pulsation dampener,and a second filter to provide pressurized reductant to a meteringvalve. Doser 114 may further include a bypass line around the pumphaving a bypass valve which is operable to open and close to permit orprevent the flow of reductant through the bypass line to a locationupstream of the first filter screen where it may be returned to thestorage tank 116, for example, during a purging operation. Doser 114 mayfurther include a blending chamber that receives reductant from themetering valve at a controllable rate. The blending chamber alsoreceives a flow of pressurized air from an air supply and discharges acombined flow of pressurized air and reductant at an outlet of doser114. The air supply may be integral to a vehicle, integral to an engine,or may be an air supply dedicated to system 100. It shall be understoodthat additional embodiments may utilize pressurized gases other thanair, for example, combinations of one or more inert gases.

Storage tank 116 holds a supply of aqueous reductant and is vented toallow reductant to be withdrawn at a port 120. A conduit 122 extendsfrom port 120 to an inlet port 124 of doser 114. A conduit 126 extendsfrom an outlet port 128 of doser 114 to injector 118. When doser 114operates, it draws reductant from storage tank 116 through conduit 122,and pumps the reductant through conduit 126 to injector 118. A backflowconduit (not shown) may be provided to return excess reductant tostorage tank 116.

Engine 102 further comprises a heat exchange system 130 through which aheat exchange fluid, such as engine coolant, is circulated by a pump132. A conduit 134 forms at least a portion of a heat exchange circuit136 that defines a single flow path for the heated heat exchange fluidto flow though doser 114 and storage tank 116 to heat reductant thereinby providing thermal contact of the heat exchange fluid with thereductant located in doser 114 and storage tank 116. Heat exchangesystem 130 receives heat from a heat source, such as engine 102, thatheats the heat exchange fluid in or before it enters heat exchangecircuit 136. Heat exchange system 130 may be part of the cooling systemfor engine 102 that is connected to a radiator (not shown) that receivesand rejects heat generated by operation of engine 102. Other embodimentscontemplate heat sources other than or in addition to engine 102, suchas the exhaust system, an electric heater, or other source of heat thatmaintains or rapidly heats the heat exchange fluid for use in heatingreductant delivery system 110. Furthermore, it is contemplated thatfluids other than liquid coolant may be used as the heat exchange fluid.

The continuous flow path defined by the heat exchange circuit 136extends from an outlet 138 of pump 132 to doser 114, through doser 114to storage tank 116, through storage tank 116 to doser 114, and backthrough doser 114 to an inlet 140 of pump 132. A return portion 139 ofthe flow path extends from the second outlet 115 of the doser 114 to thefirst inlet 117 of doser 114 and includes a control valve 142 and pump132 in the flow path. Conduit 134 may be comprised of a singlecontinuous conduit through doser 114, 116, or of discrete segmentsconnected to inlets and outlets of one or both of doser 114 and storagetank 116, with channels, conduits or other structures within one or bothof doser 114 and storage tank 116 that provide a continuation of theflow path therethrough.

Heat exchange circuit 136 further includes two-way control valve 142between outlet 115 of doser 114 and inlet 140 of coolant pump 132 thatis operable to regulate a flow of heat exchange fluid through heatexchange circuit 136 in accordance with control signals from controller150, discussed further below. Furthermore, in view of the configurationof the heat exchange circuit 136 and the control procedure disclosedherein, a single two-way control valve 142 and a single flow path forcirculation of the heat exchange fluid is all that is required for theheat exchange fluid to heat reductant in doser 114 and tank 116.

The flow of heat exchange fluid in heat exchange circuit 136 may becontrolled and monitored by controller 150 such as an engine controlmodule (ECM) or a doser control module (DCM). It shall be appreciatedthat the controller or control module may be provided in a variety offorms and configurations including one or more computing devices forminga whole or part of a processing subsystem having non-transitory memorystoring computer executable instructions, processing, and communicationhardware. It shall be further appreciated that controller may be asingle device or a distributed device, and the functions of thecontroller may be performed by hardware or software. The controller 150is in communication with any devices, sensors, and/or actuators asrequired to perform the functions present in a given embodiment.

Controller 150 is operatively coupled with and configured to storeinstructions in a memory which are readable and executable by controller150 to operate control valve 142 to complete one or more heat exchangecycles that heat reductant in doser 114 and storage tank 116. Controller150 is also operatively coupled and may receive a signal from atemperature sensor 152 associated with doser 114 and a temperaturesensor 154 associated with storage tank 116. Temperature sensors 152,154 are operable to provide a signal indicating the temperature of thereductant in doser 114 and storage tank 116, respectively. Temperaturesensors 152, 154 need not be in direct communication with doser 114 andstorage tank 116, and can be located at any position within reductantdelivery system 110 that provides a suitable indication of reductanttemperature in doser 114 and storage tank 116.

One embodiment of controller 150 is shown in FIG. 2. In certainembodiments, the controller 150 includes one or more modules structuredto functionally execute the operations of the controller 150. In certainembodiments, the controller 150 includes a reductant heating module 160and a control valve command module 180. The description herein includingmodules emphasizes the structural independence of the aspects of thecontroller 150, and illustrates one grouping of operations andresponsibilities of the controller 150. Other groupings that executesimilar overall operations are understood within the scope of thepresent application. Modules may be implemented in hardware and/orsoftware on computer readable medium, and modules may be distributedacross various hardware or software components. More specificdescriptions of certain embodiments of controller operations areincluded in the section referencing FIG. 2.

Certain operations described herein include operations to interpret oneor more parameters. Interpreting, as utilized herein, includes receivingvalues by any method known in the art, including at least receivingvalues from a datalink or network communication, receiving an electronicsignal (e.g. a voltage, frequency, current, or PWM signal) indicative ofthe value, receiving a software parameter indicative of the value,reading the value from a memory location on a computer readable medium,receiving the value as a run-time parameter by any means known in theart, and/or by receiving a value by which the interpreted parameter canbe calculated, and/or by referencing a default value that is interpretedto be the parameter value.

Controller 150 includes reductant heating module 160 that receives andinterprets an ambient temperature condition input 162, the temperatureof the reductant in the doser (TEMP R_(doser)) input 164 from sensor152, and the temperature of the reductant in the storage tank (TEMPR_(ST)) input 166 from sensor 154. Furthermore, reductant heating module160 interprets the minimum reductant temperature limit (T_(MIN)) 167 ofthe TEMP R_(doser) of doser 114 and/or the TEMP R_(ST) of storage tank116. Reductant heating module 160 also interprets the upper temperaturelimit (T_(U)) 168 of the TEMP R_(doser) of doser 114, the lowertemperature limit (T_(L)) 170 of TEMP R_(doser) of doser 114, and thethreshold temperature (T_(th)) 172 of the TEMP R_(ST) of the storagetank 116. Controller 150, as discussed further below, is configured toperform one or more heat exchange cycles which include a circulationperiod where heat exchange fluid is circulated to increase TEMPR_(doser) and a termination period where heat exchange fluid circulationis stopped to allow TEMP R_(doser) to cool.

T_(MIN) 167 is a predetermined minimum temperature of the reductant inthe doser 114 and/or storage tank 116, below which a heat exchange cycleof reductant heating is initiated by starting a circulation period ofthe heat exchange fluid. T_(U) 168 of TEMP R_(doser) of doser 114 is apredetermined maximum temperature of the reductant in the doser 114 atwhich the current circulation period of the heat exchange fluid isterminated to prevent overheating of the reductant in the doser 114,while T_(L) 170 of TEMP R_(doser) of doser 114 is a predetermined lowerlimit of the temperature of reductant in doser 114 at or below thetermination period and current heat exchange cycle is terminated, andupon which another heat exchange cycle can be initiated with a secondcirculation period of heat exchange fluid to heat the reductant in doser114 while heating the reductant in storage tank 116. T_(MIN) 167 may bethe same as or less than T_(L) 170. T_(th) 172 of TEMP R_(ST) of storagetank 116 is the threshold temperature above which further heating ofreductant in storage tank 116 is not required, terminating the heatexchange cycles until TEMP R_(doser) of doser 114 and/or TEMP R_(ST) ofstorage tank 116 reaches T_(MIN) 167. Thus, depending on the reductanttemperature, the heat exchange cycles can occur back-to-back with notime delay or have a time delay therebetween.

Reductant heating module 160 is configured to receive the variousoperational inputs 162, 164, 166 and predetermined inputs 167, 168, 170,172 and determine whether a heating of the reductant in one or both ofdoser 114 and storage tank 116 is required, which generates a heatexchange fluid demand output 182. Control valve command module 180 isconfigured to receive the heat exchange fluid demand 182 and provide acontrol valve command 184 to operate control valve 142 to an on positionto initiate a heat exchange cycle when circulation of heat exchangefluid in circuit 136 is demanded, or operate control valve 142 to an offposition when circulation of heat exchange fluid in circuit 136 is notdemanded during a termination period or between heat exchange cycles.

With reference to FIG. 3 there is illustrated a flow diagram of anexemplary heating procedure 200 for reductant delivery system 110 thatis put in operation by programming into controller 150 for use in, forexample, system 100. Procedure 200 begins at operation 202 in which acontrol routine for reductant heating of reductant delivery system 110is started. Operation 202 can begin by interpreting a key-on eventand/or by interpretation of an ambient temperature input 162 that isbelow a predetermined threshold ambient temperature. Operation 202 mayalternatively or additionally include interpreting a communication orother parameter indicating that operations of the reductant deliverysystem 110 is going to resume after a shutdown, or after a period ofinactivity of a specified length that may not include a completeshutdown. If an engine system key-on event or other initiation conditionis interpreted to be true, procedure 200 proceeds to operation 204. Ifan engine system key-on event is interpreted to be false, operation 202repeats.

Operation 204 interprets TEMP R_(doser) input 164, and storage tank TEMPR_(ST) input 166. At conditional 206, procedure 200 determines if inputs164, 166 indicate that heat exchange fluid is demanded in one or both ofdoser 114 and storage tank 116 for heating. For example, if TEMPR_(doser) input 164, and storage tank TEMP R_(ST) input 166 of one orboth of doser 114 and storage tank 116 is less than a minimumtemperature T_(MIN), then reductant heating can be demanded and a heatexchange cycle is initiated. If conditional 206 is negative, procedure200 returns to operation 204 for continued monitoring of the reductanttemperature for a heat exchange fluid demand. Alternatively, procedure200 can terminate if ambient conditions and reductant temperatureconditions indicate that reductant heating will not be required duringthe particular key-on event.

If conditional 206 is affirmative, procedure 200 continues at operation208 where control valve 142 is commanded to an open condition toinitiate a first circulation period within the first heat exchange cycleby circulating the heat exchange fluid in heat exchange circuit 136.Since heat exchange circuit 136 provides a continuous flow path thatextends serially from doser 114 to storage tank 116, reductant solutionin doser 114 and storage tank 116 are both heated by circulation of theheat exchange fluid. However, since doser 114 typically contains asmaller volume of reductant than storage tank 116, and first receivesthe heated heat exchange fluid, the reductant in doser 114 will heatmore quickly, and cool more quickly during the termination period, thanthe reductant in storage tank 116. In another embodiment, the heatexchange circuit 136 is configured to provide a continuous flowpath thatextends serially from the heat source to the storage tank 116, throughthe storage tank 116, from the storage tank 116 to doser 114, andthrough the doser 114.

During circulation of the heated heat exchange fluid in heat exchangecircuit 136, controller 150 continues to monitor TEMP R_(doser) input164. At conditional 210 it is determined of TEMP R_(doser) input 164 isapproximately equal to an upper temperature limit T_(U). If TEMPR_(doser) input 164 is less than upper temperature limit T_(U),procedure 200 returns to operation 208 and continues to circulate heatexchange fluid through heat exchange circuit 136. If TEMP R_(doser)input 164 is approximately equal to or greater than upper temperaturelimit T_(U), procedure 200 continues at operation 212 where controlvalve 142 is closed, initiating a termination period of the heatexchange cycle and ending the circulation period of heat exchange fluidin heat exchange circuit 136.

From operation 212 procedure 200 continues at conditional 214 where itis determined if storage tank TEMP R_(ST) input 166 is greater than athreshold temperature T_(th). If conditional 214 is affirmative,procedure 200 returns to operation 202 where the heat exchange cycle isterminated and procedure 200 continues until terminated by a key-offevent or other termination condition at operation 220, or by initiatinganother heat exchange cycle when indicated at conditional 206 asdiscussed above.

If conditional 214 is negative, procedure 200 continues at operation 216where controller 150 continues to monitor TEMP R_(doser) input 164during the termination period of the first heat exchange cycle. Atconditional 210 it is determined of TEMP R_(doser) input 164 isapproximately equal to or less than a lower temperature limit T_(L).When TEMP R_(doser) input 164 is greater than lower temperature limitT_(L), procedure 200 returns to operation 216 and continues to monitorthe temperature of the reductant in the doser during the first heatexchange cycle while maintaining the termination period by notcirculating heat exchange fluid through heat exchange circuit 136. IfTEMP R_(doser) input 164 is approximately equal to or less than lowertemperature limit T_(L), the first heat exchange cycle ends andprocedure 200 continues at operation 208 where control valve 142 iscommanded open to initiate a second heat exchange cycle with a secondcirculation period to circulate heat exchange fluid in heat exchangecircuit 136. Procedure 200 then continues as discussed above to completeone or more heat exchange cycles of the heat exchange fluid until thetemperature of the reductant in the storage tank reaches thresholdtemperature T_(th).

FIGS. 4A-D illustrate a graphical example of procedure 200 in operationwith system 100 over a time period that is depicted along the horizontalaxis and, except for FIG. 4D, a temperature that is depicted along thevertical axis of each Figure. FIG. 4D shows the on condition 310 and theoff 312 condition of control valve 142 over the time period, while FIG.4A illustrates a temperature 314 of the heat exchange fluid over thetime period. The temperature 314 of the heat exchange fluid is shown asa generally constant temperature, but fluctuations are also possible asthe heat exchange fluid is cooled as it passes through doser 114 andstorage tank 116 and as it is heated by the heat source.

In FIG. 4B, the TEMP R_(doser) 320 is shown fluctuating between T_(L)where a circulation period 304 of the heat exchange fluid is initiatedby opening control valve 142 and T_(U) where the circulation period ofthe heat exchange fluid is terminated by closing control valve 142 tostart a termination period 302 in the heat exchange cycle 300. FIG. 4Cshows the storage tank TEMP R_(ST) 322 increasing in response to theheat exchange fluid being circulated in circulation period 304 tomaintain TEMP R_(doser) 320 between its upper and lower limits T_(U) andT_(L). Since the storage tank 116 contains a larger volume of reductant,its cooling rate during the termination period 302 (where control valve142 is closed) is less than the cooling rate of the reductant in doser114. When TEMP R_(doser) 320 is approximately T_(L), the storage tankTEMP R_(ST) 322, while lower than its previous peak when the doser TEMPR_(doser) 320 approximated T_(U), is greater than it was at the start ofthe previous heat exchange cycle 300. Therefore, the storage tank TEMPR_(ST) 322 increases from heat exchange cycle 300 to heat exchange cycle300 despite some cooling during the termination period 302 since theincrease in temperature is greater than the decrease in temperature ineach cycle 300 while doser TEMP R_(doser) 320 is maintained betweenupper and lower limits T_(U) and T_(L).

In one embodiment, once storage tank TEMP R_(ST) 322 reaches a thresholdtemperature T_(th), control valve 142 need not be cycled to maintaindoser TEMP R_(doser) 322 between T_(U) and T_(L). Rather, a minimum lowtemperature threshold such as T_(MIN) can be provided for TEMP R_(doser)322 that allows the reductant temperature to drop to a lower temperaturethan T_(L) before initiating a new heat exchange cycle 300, to avoidoverheating or unnecessary heating of reductant in storage tank 116.

Certain exemplary embodiments will now be further described. Certainexemplary embodiments comprise systems for heating a reductant deliverysystem that is connected to an exhaust aftertreatment system. Certainexemplary systems include a reductant storage tank configured to store areductant for treatment of an exhaust gas produced by an internalcombustion engine; a doser configured to receive reductant from thestorage tank and deliver a quantity of reductant for injection into theexhaust gas; a heat exchange circuit defining a flow path for a heatexchange fluid so that the heat exchange fluid flows through the doserfor thermal contact with reductant in the doser, from the doser to thestorage tank, through the storage tank for thermal contact withreductant in the storage tank, from the storage tank to the doser, andback through the doser to a return loop for return to the doser; and acontrol valve in the return loop of the heat exchange circuit operableto regulate a flow of the heat exchange fluid in the flow path.

In some embodiments, the heat exchange circuit further includes a heatsource in the return loop to heat the heat exchange fluid before theheat exchange fluid returns to the doser. In one refinement, the heatsource is the internal combustion engine and the heat exchange fluid isa coolant that receives heat from operation of the internal combustionengine. In another refinement, the control valve is located in the heatexchange circuit after the storage tank. In other embodiments, thesystem further comprises a pump to circulate the heat exchange fluid inthe heat exchange circuit. In some embodiments, the reductant is a ureasolution. In other embodiments, the heat exchange circuit defines asingle flow path for the heat exchange fluid. In still otherembodiments, the control valve consists of a single two-way controlvalve in the heat exchange circuit.

In some embodiments, the system also includes an injector connected tothe exhaust system and the doser is connected to the injector. In otherembodiments, the heat exchange fluid in the portion of the flow paththat extends back through the doser to the return loop is in thermalcontact with reductant in the doser.

Certain exemplary systems also include an internal combustion enginehaving an exhaust system for receiving an exhaust gas produced fromoperation of the internal combustion engine; a reductant delivery systemthat includes a reductant storage tank and a reductant doser, whereinthe storage tank stores a reductant that is provided to the doser fordelivery into the exhaust system for treatment of the exhaust gas; and aheat exchange system including a heat exchange circuit configured toprovide a flow path for a heat exchange fluid that is heated at least inpart by operation of the internal combustion engine. The flow path isarranged to circulate the heat exchange fluid to thermally contact theheat exchange fluid with the reductant in the doser before thermallycontacting the heat exchange fluid with the reductant in the storagetank. The heat exchange system further includes a control valve in theflow path to control circulation of the heat exchange fluid.

In certain embodiments, the flow path extends through the doser, fromthe doser to the storage tank, through the storage tank, from thestorage tank to the doser, and back through the doser to a return loopfor return to the doser. In other embodiments, the reductant is a ureasolution and the system includes an injector connected to the exhaustsystem and the doser is connected to the injector. In certainrefinements of these embodiments, the exhaust system includes aselective catalytic reduction (SCR) catalyst and the injector isconnected to the exhaust system upstream of the SCR catalyst.

In other embodiments, the system includes a pump that is operable tocirculate the heat exchange fluid through the flow path of the heatexchange circuit. In some embodiments, the heat exchange circuit definesa single flow path for the heat exchange fluid. In other embodiments,the control valve consists of a single two-way control valve in the flowpath.

Certain exemplary systems also includes an internal combustion enginefor combusting fuel and producing an exhaust stream; an exhaust systemconnected to the internal combustion engine for receiving the exhauststream and conveying the exhaust stream to atmosphere, the exhaustsystem including a selective catalytic reduction (SCR) catalystconfigured to convert NOx emissions in the exhaust stream in thepresence of a reductant injected into the exhaust system upstream of theSCR catalyst; a storage tank for holding a supply of the reductant; adoser for receiving the reductant from the storage tank and fordelivering a quantity of reductant for injection to the exhaust system;and a heat exchange circuit providing a flow path for a heat exchangefluid. The flow path includes a return portion in which the heatexchange fluid is heated at least in part from operation of the internalcombustion engine. The flow path further forms a uni-directional flowdirection for the heat exchange fluid that extends from the returnportion through the doser, from the doser through the storage tank, andfrom the storage tank through the doser to the return portion. The flowpath places the heat exchange fluid that is heated from the internalcombustion engine in heat exchange relationship first with reductant inthe doser and then with the reductant in the storage tank.

In certain embodiment, the system also includes a control valve in thereturn portion to regulate flow of the heat exchange fluid in the flowpath.

Certain exemplary systems also include an internal combustion enginehaving an exhaust system for receiving an exhaust gas produced fromoperation of the internal combustion engine and a reductant deliverysystem that includes a reductant storage tank and a reductant doser. Thestorage tank stores a reductant that is provided to the doser fordelivery to the exhaust system for treatment of the exhaust gas producedby operation of the internal combustion engine. The systems also includea heat exchange system including a heat exchange circuit configured toprovide a flow path for a heat exchange fluid to heat the reductant. Theflow path is arranged to circulate the heat exchange fluid to thermallycontact heated heat exchange fluid with the reductant in the doser andreductant in the storage tank. The heat exchange system also includes acontrol valve in the flow path to control a flow of the heat exchangefluid in the supply line. The systems further include a controllerconnected to the control valve that is operable to open and close thecontrol valve to control circulation of the heat exchange fluid in theflow path. The controller is configured to initiate a first circulationperiod of the heated heat exchange fluid in the flow path through thedoser and then through the storage tank to increase a temperature of thereductant in the doser and the storage tank when the temperature of thereductant in at least one of the doser and the storage tank is less thana predetermined minimum temperature; terminate the first circulationperiod of the heat exchange fluid when the temperature of the reductantin the doser reaches an upper temperature limit; and initiate a secondcirculation period of the heat exchange fluid in the heat exchangecircuit after the first circulation period when the temperature of thereductant in the doser reaches a lower temperature limit to increase thetemperature of the reductant in the doser and the storage tank.

In certain embodiments, the controller is configured to continue thesecond circulation period of the heat exchange fluid until thetemperature of the reductant in the doser reaches the upper temperaturelimit. The temperature of the reductant in the storage tank is greaterat an end of the second circulation period than at an end of the firstcirculation period. In other embodiments, the controller is configuredto determine the temperature of the reductant in the storage tank isless than a threshold temperature before initiating the secondcirculation period.

Certain exemplary embodiments are methods associated with heating ofreductant in a reductant delivery system. Certain exemplary methodsinclude interpreting a temperature of a reductant in a reductantdelivery system, the reductant delivery system including a storage tankfor storing a source of reductant and a doser for receiving thereductant from the storage tank and providing a measured quantity of thereductant for delivery to an exhaust system of an internal combustionengine; heating a heat exchange fluid with a heat source; when thetemperature of the reductant in at least one of the doser and thestorage tank is less than a predetermined minimum temperature,initiating a first circulation period of the heated heat exchange fluidthrough the doser and then through the storage tank to increase atemperature of the reductant in the doser and the storage tank;terminating the first circulation period of the heat exchange fluid whenthe temperature of the reductant in the doser reaches an uppertemperature limit; and after terminating the first circulation period ofthe heat exchange fluid, initiating a second circulation period of theheat exchange fluid in the heat exchange circuit when the temperature ofthe reductant in the doser reaches a lower temperature limit to increasethe temperature of the reductant in the doser and the storage tank.

In some embodiments, terminating the first circulation period of theheat exchange fluid includes closing a control valve in a flow path ofthe heat exchange fluid. In other embodiments, the method includescontinuing the second circulation period of the heat exchange fluiduntil the temperature of the reductant in the doser reaches the uppertemperature limit. In refinements of this embodiment, the temperature ofthe reductant in the storage tank is greater at an end of the secondcirculation period at an end of the first circulation period. In otherembodiments, the predetermined minimum temperature is less than thelower temperature limit. In still other embodiments, the heat source isthe internal combustion engine, the reductant is a urea solution, and/orthe exhaust system includes a selective catalytic reduction catalyst.

In some embodiments, the method includes determining the temperature ofthe reductant in the storage tank is less than a threshold temperaturebefore initiating a third circulation period after the secondcirculation period. In other embodiments, the method includesterminating the second circulation period of the heat exchange fluidwhen the temperature of the reductant in the doser reaches the uppertemperature limit; and, after terminating the second circulation periodof the heat exchange fluid, initiating a third circulation period of theheat exchange fluid in the heat exchange circuit when the temperature ofthe reductant in the doser reaches the lower temperature limit toincrease the temperature of the reductant in the doser and the storagetank.

In other embodiments, the method includes terminating and initiating aplurality of recirculation periods of the heat exchange fluid in theheat exchange circuit until the temperature of the reductant in thestorage tank reaches a predetermined threshold temperature. Inrefinements of this embodiment, when the temperature of the reductant inthe storage tank reaches the predetermined threshold temperature, themethod includes initiating another circulation period when thetemperature of the reductant in at least one of the doser and thestorage tank is less than the predetermined minimum temperature.

Certain exemplary methods further includes heating a reductant in areductant delivery system that is operable to deliver a reductant forinjection into an exhaust system connected to an engine. Heating thereductant includes completing a plurality of heat exchange cycles with aheat exchange fluid flowing in a flow path that extends through thereductant delivery system. At least one of the heat exchange cyclesincludes increasing a temperature of the reductant in a doser of thereductant delivery system while increasing a temperature of thereductant in a storage tank of the reductant delivery system bycirculating the heat exchange fluid from the doser to the storage tank;terminating circulation of the heat exchange fluid when the temperatureof the reductant in the doser reaches an upper limit; and ending acurrent heat exchange cycle when the temperature of the reductant in thedoser drops from the upper limit to a lower limit. The temperature ofthe reductant in the doser drops at a first rate from the upper limit tothe lower limit and the temperature of the reductant in the storage tankdrops at a second rate that is slower than the first rate.

In some embodiments of the method, the temperature of the reductant inthe storage tank is increased from the end of one heat exchange cycle tothe next. In other embodiments, completing the plurality of heatexchange cycles includes ending a last one of the heat exchange cycleswhen the temperature of the reductant in the storage tank reaches athreshold temperature. In still other embodiments, terminatingcirculation of the heat exchange fluid includes closing a control valvein the flow path. In some embodiments, the method includes heating theheat exchange fluid in the flow path. In other embodiments, the flowpath extends serially from a heat source to the doser, through thedoser, from the doser to the storage tank, and through the storage tank.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly certain exemplary embodiments have been shown and described andthat all changes and modifications that come within the spirit of theinventions are desired to be protected. It should be understood thatwhile the use of words such as preferable, preferably, preferred or morepreferred utilized in the description above indicate that the feature sodescribed may be more desirable, it nonetheless may not be necessary andembodiments lacking the same may be contemplated as within the scope ofthe invention, the scope being defined by the claims that follow. Inreading the claims, it is intended that when words such as “a,” “an,”“at least one,” or “at least one portion” are used there is no intentionto limit the claim to only one item unless specifically stated to thecontrary in the claim. When the language “at least a portion” and/or “aportion” is used the item can include a portion and/or the entire itemunless specifically stated to the contrary.

The invention claimed is:
 1. A method, comprising: interpreting atemperature of a reductant in a reductant delivery system, the reductantdelivery system including a storage tank for storing a source ofreductant, a doser for receiving the reductant from the storage tank andproviding a measured quantity of the reductant for delivery to anexhaust system of an internal combustion engine, and an injector forinserting the reductant received from the doser into the exhaust system;heating a heat exchange fluid in a heat exchange circuit with a heatsource, the heat exchange circuit including a conduit providing a singlecontinuous uni-directional flow path that extends serially from a heatsource to the storage tank, through the storage tank, from the storagetank to the doser, through the doser and back to the heat source in aclosed loop, the heat exchange circuit fluidly isolated from theinjector; when the temperature of the reductant in at least one of thedoser and the storage tank is less than a predetermined minimumtemperature, initiating a first circulation period of the heated heatexchange fluid in the heat exchange circuit by selectively opening acontrol valve positioned in the flow path of the heat exchange fluid,the heat exchange fluid flowing through the doser and then through thestorage tank to increase a temperature of the reductant in the doser andthe storage tank; terminating the first circulation period of the heatexchange fluid by selectively closing the control valve when thetemperature of the reductant in the doser reaches an upper temperaturelimit; and after terminating the first circulation period of the heatexchange fluid, initiating a second circulation period of the heatexchange fluid in the heat exchange circuit when the temperature of thereductant in the doser reaches a lower temperature limit to increase thetemperature of the reductant in the doser and the storage tank.
 2. Themethod of claim 1, further comprising continuing the second circulationperiod of the heat exchange fluid in the heat exchange circuit until thetemperature of the reductant in the doser reaches the upper temperaturelimit.
 3. The method of claim 2, wherein the temperature of thereductant in the storage tank is greater at an end of the secondcirculation period than at an end of the first circulation period. 4.The method of claim 1, wherein the predetermined minimum temperature isless than the lower temperature limit.
 5. The method of claim 1, whereinthe heat source is the internal combustion engine.
 6. The method ofclaim 1, wherein the reductant is a urea solution and the exhaust systemincludes a selective catalytic reduction catalyst.
 7. The method ofclaim 1, further comprising determining the temperature of the reductantin the storage tank is less than a threshold temperature beforeinitiating a third circulation period after the second circulationperiod.
 8. The method of claim 1, further comprising: terminating thesecond circulation period of the heat exchange fluid when thetemperature of the reductant in the doser reaches the upper temperaturelimit; and after terminating the second circulation period of the heatexchange fluid, initiating a third circulation period of the heatexchange fluid in the heat exchange circuit when the temperature of thereductant in the doser reaches the lower temperature limit to increasethe temperature of the reductant in the doser and the storage tank. 9.The method of claim 1, further comprising: terminating and initiating aplurality of recirculation periods of the heat exchange fluid in theheat exchange circuit until the temperature of the reductant in thestorage tank reaches a predetermined threshold temperature.
 10. Themethod of claim 9, wherein when the temperature of the reductant in thestorage tank reaches the predetermined threshold temperature, initiatinganother circulation period when the temperature of the reductant in atleast one of the doser and the storage tank is less than thepredetermined minimum temperature.
 11. The method of claim 1, whereinthe control valve includes a two-way control valve.
 12. A method,comprising: heating a reductant in a reductant delivery system that isoperable to deliver a reductant for injection into an exhaust systemconnected to an engine, wherein heating the reductant includescompleting a plurality of heat exchange cycles with a heat exchangefluid in a heat exchange circuit, the heat exchange circuit including aconduit providing a single continuous uni-directional flow path thatextends serially from a heat source to a storage tank, through thestorage tank, from the storage tank to a doser, through the doser andback to the heat source in a closed loop, the heat exchange circuitfluidly isolated from an injector, wherein at least one of the heatexchange cycles includes: increasing a temperature of the reductant inthe doser of the reductant delivery system while increasing atemperature of the reductant in a storage tank of the reductant deliverysystem by circulating the heat exchange fluid in the heat exchangecircuit from the doser to the storage tank via selectively opening acontrol valve positioned in a flow path of the heat exchange fluid;terminating circulation of the heat exchange fluid when the temperatureof the reductant in the doser reaches an upper limit by selectivelyclosing the control valve; and ending a current heat exchange cycle whenthe temperature of the reductant in the doser drops from the upper limitto a lower limit, wherein the temperature of the reductant in the doserdrops at a first rate from the upper limit to the lower limit and thetemperature of the reductant in the storage tank drops at a second ratethat is slower than the first rate.
 13. The method of claim 12, whereinthe temperature of the reductant in the storage tank increases from theend of one heat exchange cycle to the next.
 14. The method of claim 12,wherein completing the plurality of heat exchange cycles includes endinga last one of the heat exchange cycles when the temperature of thereductant in the storage tank reaches a threshold temperature.
 15. Themethod of claim 12, further comprising heating the heat exchange fluidin the flow path.
 16. The method of claim 12, wherein the control valveincludes a two-way control valve.